Barley grass is an emerging forage potentially helping relieve the lack of green forage for livestock, and its nutritive value is influenced by kinds of cultivation conditions. This study was conducted to investigate the effect of cultivation temperature (25 °C vs. 30 °C) and seed sterilization (0.2% NaClO) on the dynamic changes in nutrient component, fermentation potential and bacterial community of hydroponic barley grass. The results showed that starch content (56.67%) in the barley grass gradually declined and cell wall components, crude protein, and ash concentrations increased, with 26–35% dry matter loss by 10 days of cultivation, where a higher cultivation temperature (30 °C) resulted in a higher fiber concentration (NDF 29.82% vs. 19.44%; ADF 12.57% vs. 8.02%) and a lower starch content (19.69% vs. 32.05%) while seed sterilization treatment resulted in an opposite result along with an improved dry matter recovery (73.33% vs. 70.15%). Furthermore, seed sterilization increased in vitro rumen gas production (GP<sub>48</sub> 55.97 vs. 50.50 mL/0.2 g DM) of the resulting barley grass, and its fermentation potential by 10 days of cultivation was much lower than that by 8 days. Bacterial diversity analysis revealed that seed sterilization decreased the richness and diversity of bacterial community, and the abundance of taxa <i>Methyloversatilis</i>, <i>Parabacteroides</i>, <i>Phascolarctobacterum</i>, <i>Lactococcus</i>, <i>Pseudomonas</i> might account for the difference in nutrient component. It is suggested that optimizing cultivation conditions like temperature and sterilization could significantly improve nutrient value and dry matter recovery of hydroponic barley grass, and the production cycle of hydroponic barley grass is no better if more than 8 days, where the bacterial community plays an indispensable role.
Abstract Private imports of alcoholic beverages—often referred to as cross-border trade—have long raised concerns in Sweden and other Nordic countries due to their potential impact on national alcohol policies and public health. A key concern is that this trade increases total alcohol consumption and related harms. This study examines the relationship between private alcohol imports and domestic sales in Sweden, with a focus on how cross-border trade influences total alcohol consumption. Using regional and beverage-specific time series data from 2002 to 2023, we applied SARIMA modelling to self-reported import estimates from the Monitor project to assess substitution effects on domestic alcohol sales. Private imports significantly displace domestic alcohol purchases, particularly in southern Sweden across all beverages, though the substitution is partial. For Sweden as a whole, analyses indicate that a 1-litre increase in imports is associated with a 0.456-litre decrease in domestic sales. In central Sweden, only spirits imports show a significant effect (1-litre increase in spirits imports yields a 0.175-litre decrease in domestic sprits sales), while no significant associations are observed in the north. The findings suggest that cross-border trade contributes to higher overall alcohol consumption, especially in border regions. Regional variation underscores the need for differentiated alcohol policy responses. Private imports undermine the effectiveness of domestic alcohol control measures. However, since domestic sales do not influence import levels, policy efforts such as increased excise taxation may reduce total consumption without triggering substantial compensatory imports.
Gembili tubers (Dioscorea esculenta) are abundant in Indonesia but remain underutilised despite their potential as a functional food. One effort that has been made is to produce a symbiotic fermented beverage, as it is known to contain prebiotic inulin that can be fermented using probiotics. Lactobacillus plantarum B1765 is charactherized by its probiotic potential. This research evaluated the impact of fermentation duration using L. plantarum B1765 starter culture on the quality of gembili juice products, including Total Lactic Acid Bacteria (LAB), pH, Total Titratable Acids (TTA), and organoleptic quality. Gembili juice was made by fermenting gembili juice at 37°C for 0, 6, 12, 18, 24, and 36 hours. The total LAB count was enumerated using the total plate count (TPC) method with MRS-Agar medium containing CaCO3. pH determination was performed using a pH meter. TTA was calculated by acid-base titration, and organoleptic quality was assessed by untrained panellists, who rated the level of liking using a hedonic scale. The total LAB and pH data were analyzed using the Kruskal–Wallis test, while the TTA data were analyzed using a one-way ANOVA to determine the significant differences among the fermentation durations. The fermentation time of gembili fermented beverages had an effect (p < 0.05) on the total number of LAB, pH, and TTA. LAB growth increased and reached an optimum of 7.55 x 10⁸ CFU/mL at 18 hours. However, the pH continued to decrease to 3.84, and the TTA continued to increase to 0.32% until the end of fermentation. Sensory evaluation (hedonic test) showed that fermentation time had no effect (p>0.05) on color and aroma. Still, it had an impact (p < 0.05) on taste, with the highest preference for the 18-hour fermentation. This product complies with SNI standards and is suitable for development as a fermented functional beverage. The inulin and phenolic compounds present in gembili may contribute to its antioxidant activity and α-glucosidase inhibitory effects.
Akeyt Richmond Hervé Koffi, Alessio Campitelli, Daniel Stanojkovski
et al.
Leachate management remains a major environmental challenge, especially in rapidly urbanizing cities of developing countries. Traditionally considered toxic and useless, it is a sustainable organic resource with the potential for high-value biochemical production through bioprocessing. This study investigated the characteristics of fresh leachates from three solid waste transfer stations (SWTS) in the Abidjan district, Côte d’Ivoire, and assessed their potential as substrates for medium-chain fatty acid (MCFA) production via microbial chain elongation. The MCFA synthesis was carried out in anaerobic bioreactors operated under methanogenesis inhibition conditions. The leachates from Bingerville, Abobo-Dokui, and Yopougon exhibited acidic and high organic content, particularly volatile fatty acids (VFAs), key precursors for MCFA synthesis. High concentrations of microbial communities associated with chain elongation were observed, including <i>Clostridium</i> (sulphite-reducing), <i>Lactobacillus, Bacillus, and Pseudomonas</i> (greater than 5 log10 CFU/mL). MCFA production ranged from 5 to 10 g/L, mainly C6, C7, and C8, with compositional variation depending on the SWTS. Notably, leachates from higher-income areas demonstrated higher MCFA productivity compared to those from lower-income areas. These findings highlight the potential of fresh SWTS leachates in the Abidjan district for sustainable MCFA production, paving the way for industrial applications.
Ryon W. Springer, Trinette N. Jones, Michaela R. Plowman
et al.
Ruminant in vitro methodologies use washing with neutral detergent solution (NDS) after incubation to mimic ruminant digestion, which is physiologically different compared to that of horses. Our objectives were to determine if washing feed samples with NDS before in vitro fermentation (PRE) would suppress fiber digestion versus a post-incubation wash (POST), and to compare in vitro digestibility of forage-based feed mixtures with added soluble carbohydrates (CARB), soluble protein (PROT), or soluble carbohydrates and soluble protein (C + P) to only-forage samples (CONT). Dried, ground feed mixtures sealed in ANKOM filter bags were placed in Daisy<sup>II</sup> incubators for 48 h in a split–split-plot batch culture design. Digestibility was determined as in vitro neutral detergent fiber digestibility (IVNDFD), in vitro acid detergent fiber digestibility (IVADFD), in vitro hemicellulose digestibility (IVHD), and in vitro true digestibility (IVTD). The PRE treatment decreased IVHD for CARB versus POST (<i>p</i> = 0.007). Pooling all mixtures, PRE decreased IVTD (<i>p</i> = 0.001), IVADFD (<i>p</i> = 0.036), and IVHD (<i>p</i> = 0.001) and tended to decrease IVNDFD (<i>p</i> = 0.072). The CARB mixture increased IVTD versus all other mixtures (<i>p</i> < 0.001). Pre-washing with NDS suppressed in vitro fermentation by removing soluble carbohydrates. Without removal of soluble carbohydrates to mimic in vivo digestion, fiber digestibility is likely overestimated.
Withering is a crucial step in tea production that reduces the moisture content and induces biochemical changes in tea leaves. The withering process triggers oxidative stress by accumulating reactive oxygen species (ROS) in tea leaves. The presence of flavonol glycosides is crucial for tea quality and tea's stress response to environmental changes pre- and post-harvest. However, the role of flavonol glycosides during withering remains unexplored. The degradation of flavonol glycosides during withering is mainly attributed to the enzymatic antioxidant defense system, which produces flavonol aglycones and soluble sugars that protect leaf cells from oxidative stress. This degradation contributes to a sweeter taste and enhances the taste and aroma of tea. This review emphasizes the role of the withering process and the degradation of flavonol glycosides, highlighting their role in neutralizing ROS formation as a response to oxidative stress, and discusses how changes in flavonol glycosides contribute to the taste of tea. The importance of the withering process in the degradation of flavonol glycosides is also highlighted. Further research is needed to understand the dynamic changes of flavonol glycosides during the withering process, which is essential to improving tea quality.
Cold stress significantly impacts the growth, quality, and yield of tea plant leaves. Additionally, silicon (Si) is a widely abundant element on earth and is recognized for its beneficial effect on plant growth and development. Here, a comprehensive transcriptomic, biochemical, and metabolomic investigations on tea plant leaves was conducted, examining the impact of Si-mediated improvement during short- (1 d), medium- (3 d), and long-term (5 d) exposure to cold stress. Biochemical and physiological analyses demonstrated that Si-mediated amelioration enhanced the activity of protective enzyme systems during all three cold stress treatments. There was a marked increase in soluble sugar content and a significant decrease in chlorophyll B content during the medium-term cold stress. Integrated transcriptomic and metabolomic analyses revealed that the differentially expressed genes (DEGs) primarily targeted pathways in phenylpropane biosynthesis, α-linolenic acid metabolism, pentose and glucuronic acid interconversion, and nitrogen metabolism. Similarly, differentially abundant metabolites (DAMs) linked to cold stress response in tea plants predominantly involved flavone and flavonol biosynthesis, flavonoid biosynthesis, aminoacyl-tRNA biosynthesis, galactose metabolism, and phenylpropanoid biosynthesis. The integrated analysis of the metabolites associated with these pathways and expression profiles further confirmed the involvement of the identified DEGs in responding to cold stress and the beneficial effect of Si in tea plants. This research expands our knowledge of the regulatory networks underlying cold stress responses in tea plants.
Mitigating enteric methane emissions through diet formulation remains a significant challenge in cattle nutrition. This study developed a system to evaluate the methane production potential of feeds, expressed as the effective ruminal methane production rate (eRMR, mL/g dry matter [DM]), using a discontinuous in vitro ruminal fermentation system using rumen fluid. Sixteen concentrate feeds and two forages were tested, with a reference diet (ryegrass straw:corn:corn gluten feed = 1:1:1) included in each batch to standardize conditions and account for associative effects among feeds. Test feeds were incubated with the reference diet in closed bottles under strictly anaerobic conditions. Methane and total gas production were measured at 2, 4, 6, and 24 h, and true dry matter digestibility was calculated after 6 and 24 h. For each batch, sample feed values were corrected and standardized using those of the reference diet. The eRMR value was calculated by integrating a differential equation with parameters incorporating ruminal digestion and passage dynamics. The test feed eRMR values ranged from 1.2 mL/g DM (soybean meal) to 56.7 mL/g DM (soybean hull), with the reference diet at 14.8 mL/g DM. Evaluation of feed eRMR using data from two in vivo studies demonstrated strong correlations between predicted diet-specific eRMR values and measured methane emissions from Hanwoo steers (r = 0.93 and 0.85). This system, incorporating rumen dynamics with a reduced sampling schedule, provides a precise and practical tool for predicting in vivo enteric methane production and optimizing diet formulations to mitigate methane emissions from cattle.
Alfalfa silage has a high proportion of rumen-degradable protein content. Increasing dietary rumen-degradable starch (RDS) can enhance ruminal microbial protein synthesis. This study was conducted to investigate the influence of RDS levels in substrates with alfalfa silage on in vitro rumen fermentation and nitrogen (N) utilization. Rumen fluid was collected and dispensed into anaerobic fermentation bottles, each containing 1 g of substrate and 60 mL of rumen fluid–buffer mixture. The substrate was composed of 40% alfalfa silage and five different RDS levels: 14.85% RDS, 16.40% RDS, 18.67% RDS, 20.21% RDS, and 21.62% RDS. For each RDS level, three replicates were prepared. Each substrate was then incubated at 39 °C for 3, 6, 12, and 24 h. After incubation, the following parameters were measured: gas production, pH, α-amylase activity, ammonia nitrogen (NH<sub>3</sub>-N), bacterial protein (BCP), and short-chain fatty acid (SCFA) concentrations were measured. Total gas production increased linearly with increasing RDS levels from 3 to 10 h of incubation (<i>p</i> < 0.01), with no difference observed among five levels after 11 h. At 3 h of incubation, pH decreased linearly with increasing RDS levels (<i>p</i> < 0.05). BCP concentrations and α-amylase activity increased linearly or quadratically with increasing RDS levels (<i>p</i> < 0.01), while the R4 group had the highest concentrations of BCP and the R5 group had the highest activity of α-amylase (<i>p</i> < 0.01). At 6 h of incubation, the NH<sub>3</sub>-N concentration decreased linearly or quadratically with increasing RDS levels (<i>p</i> < 0.05), and the α-amylase activity, acetate, propionate, and total SCFA concentrations increased linearly (<i>p</i> < 0.01). The R4 group had the highest activity of α-amylase (<i>p</i> < 0.01), and the R5 group had the highest concentrations of acetate (<i>p</i> < 0.05) and propionate (<i>p</i> < 0.01). At 12 h of incubation, BCP, NH<sub>3</sub>-N, and propionate concentrations, as well as α-amylase activity, increased linearly or quadratically with increasing RDS levels (<i>p</i> < 0.05). At 24 h of incubation, the α-amylase activity increased linearly with increasing RDS levels (<i>p</i> < 0.05). The highest multiple-factor associative effects index was observed in the 20.21% RDS substrate, indicating that an RDS level of 20.21% in the alfalfa silage substrate resulted in a desirable rumen N utilization.
Ricardo S. Aleman, Ismael Montero-Fernández, Jhunior A. Marcía
et al.
This review paper addresses vegetable fermentation from a microbiological and technological point of view, with particular emphasis on the potential of lactic acid bacteria to carry out these transformations. This review paper also covers the spectrum of traditional and emerging fermented plant foods. Fermentation with lactic acid bacteria represents an accessible and appropriate strategy to increase the daily consumption of legumes and vegetables. Often, lactic fermentation is carried out spontaneously following protocols firmly rooted in the culture and traditions of different countries worldwide. Fermented plant products are microbiologically safe, nutritious, and have pleasant sensory characteristics, and some of them can be stored for long periods without refrigeration. Controlled fermentation with selected lactic acid bacteria is a promising alternative to guarantee high-quality products from a nutritional and organoleptic point of view and with benefits for the consumer’s health. Recent advances in genomics and molecular microbial ecology predict a bright future for its application in plant fermentation. However, it is necessary to promote molecular approaches to study the microbiota composition, select starters aimed at different legumes and vegetables, generate products with nutritional properties superior to those currently available, and incorporate non-traditional vegetables.
Rattana Jariyaboon, Surananee Hayeeyunu, Nikannapas Usmanbaha
et al.
Food waste is categorized as organic solid waste, which has a negative impact on environmental sustainability. Food waste was simultaneously used for the feasible generation of mixed volatile fatty acids (VFAs) and bio-hydrogen by deploying dark fermentation. Original anaerobic digested sludge was prepared via the shock technique with 50 g/L glucose under thermophilic temperature (55 °C). The pretreated inoculum was found capable of converting 10 g VS/L food waste to hydrogen with a rather high yield of 135.2 ± 7 mL H<sub>2</sub>/VS<sub>added</sub>. The effect of various concentrations of food waste, including 10.2, 16.3, 20.3, and 26.4 g VS/L, on mixed VFAs production was subsequently carried out in batch dark fermentation. The highest butyric acid concentration (5.26 ± 0.22 g/L) in soluble metabolites was obtained from batch dark fermentation with 26.4 g VS/L of food waste. The dominant <i>Clostridium thermobutyricum, Clostridium sporogenes,</i> and <i>Octadecobacter</i> sp. found in the batch of dark fermentation of food waste could confirm the effectiveness of the load shock pretreatment method for inoculum preparation. The continuous stirred tank reactor (CSTR) inoculated with mixed cultures, also prepared via the load shock pretreatment method and without the addition of external nutrients, was operated by feeding 26.4 g VS/L food waste at the kinetically designed HRT for 4 days, corresponding to an organic loading rate (OLR) of 7.6 g VS/L·d. Under steady state conditions, promising butyric acid (5.65 ± 0.51 g/L)-rich mixed VFAs were achieved along with the hydrogen yield of 104.9 ± 11.0 mL-H<sub>2</sub>/g VS<sub>added</sub>, which is similar to the upper side of the previously reported yields (8.8 ± 0.6–103.6 ± 0.6 mL-H<sub>2</sub>/g VS).
Phosphatidylserine (PS) is a natural phospholipid with particular importance in the food, cosmetic, and pharmaceutical industries. Recently, the synthesis of PS mediated by phospholipase D (PLD) has drawn great attention. But the application of free PLD is limited by various drawbacks, including its instability under extreme conditions, difficulties in reuse and recovery, and high costs. In this work, saPLD-inorganic hybrid nanoflowers (saPLD@NFs) were synthesized with PLD from <i>Streptomyces antibioticus</i> (saPLD) as the organic component and Ca<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> as the inorganic component. The saPLD@NFs demonstrated outstanding immobilization capability and achieved a 119% enzyme activity recovery rate. Furthermore, the saPLD@NFs exhibited better thermostability and pH stability in comparison to free saPLD. The PS yield of saPLD@NFs was about 57.4% in the first cycles and still reached 60.4% of its initial PS yield after four cycles. After 25 d storage at 4 °C, saPLD@NFs retained 66.5% of its original activity, but free saPLD only retained 38.3%, indicating that saPLD@NFs have excellent storage stability. Thus, this study established a new method of preparing PLD nanoflowers for effective PS synthesis, which might accelerate the practical utilization of this biocatalyst.
Vladimír Nesvadba, Jana Olšovská, Lenka Straková
et al.
The aim of the study is to evaluate the intensity and character of the beer aroma in selected hop varieties. In 2022 and 2023, new Czech Flavour hop varieties of Ceres, Pluto, and Saturn were registered. Ceres exhibits a mild citrusy and fruity hop aroma. Pluto has an intense fruity and herbal aroma, while Saturn has an intense fruity aroma with a milder citrus note. Differences in the intensity and character of the beer aroma were identified based on the hop variety used and the cold hopping dose. These varieties and their combinations were tested under cold hopping at 3 g/l and 6 g/l to assess the impartment of the aromas to beer. The combination of Pluto + Saturn shows the highest intensity of a spicy aroma, while Ceres exhibits the highest intensity of both the fruity and herbal aromas – all this at 6 g/l. The best character of the spicy aroma is observed with Ceres at 3 g/l. Ceres also demonstrates the best character of the fruity aroma, and Ceres + Pluto combination excels in the herbal aroma, both at the dose of 6 g/l. The popularity of beer is crucial, with the combination of Ceres + Pluto at 3 g/l proving to be the most popular. The results have practical applications in breweries producing bottom-fermented beers that utilize dry hopping. It is obvious which hop varieties or their combinations can be used to accentuate individual aroma profiles.
Simms A. Adu, Matthew S. Twigg, Patrick J. Naughton
et al.
Acidic sophorolipids (Acidic SL), congeners of sophorolipid biosurfactants, offer a potential alternative to synthetic sodium lauryl ether sulphate (SLES) in skincare applications. However, major challenges associated with the laboratory-based investigations of the cytotoxic effects of Acidic SL have been the utilisation of impure and/or poorly characterised congeners as well as the use of monolayers of skin cells in in vitro assays. While the former limitation makes glycolipids less attractive for use in academic research and skincare applications, the latter does not provide an accurate representation of the in vivo human skin. The present study, therefore, for the first time, assessed the cytotoxic effects of 96% pure Acidic SL on a 3D in vitro skin model in comparison with SLES, with the aim of investigating a natural alternative to synthetic surfactants for potential use in skincare applications. The 3D in vitro skin model was colonised with <i>Staphylococcus epidermidis</i> for 12 h, and afterwards treated with either Acidic SL or SLES at 100 μg mL<sup>−1</sup> for a further 12 h. Subsequently, the cytotoxic effects of Acidic SL in comparison with SLES were assessed using a combination of microbiology, molecular biology techniques, immunoassays, and histological analyses. It was demonstrated that Acidic SL had no deleterious effects on the viability of <i>S. epidermidis</i>, tissue morphology, filaggrin expression, and the production of inflammatory cytokines in comparison to SLES. These findings, in conjunction with the possibility to produce Acidic SL from cheaper renewable natural resources, demonstrate that Acidic SL could offer a potential sustainable alternative to synthetic surfactants.
<i>Mahweu</i> is an important indigenous beverage for many low-income and undernourished consumers in southern Africa. As a result, the nutritional and phytochemical profile of <i>mahewu</i> samples (obtained using optimized fermentation and boiling conditions from a previous study) as well as their related raw materials (white and yellow maize) were investigated. At these conditions, white and yellow maize <i>mahewu</i> (WM and YM) were prepared utilizing various inocula including sorghum malt, wheat, millet malt, or maize malt, and the pH, titratable acidity (TTA), total soluble solid (TSS), and proximate analysis were determined. The mineral content, amino acid composition, and phenolic compound profile were also investigated using inductive coupled plasma optical emission spectrometry (ICP-OES), high-performance liquid chromatography (HPLC), and ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF-MS), respectively. Fermentation was observed to have influenced the proximate composition of obtained <i>mahewu</i> samples compared to the raw flour with significant (<i>p</i> ≤ 0.05) improvement in protein from 8.59 to 9.7% (YM) and 8.78 to 9% (WM) as well as carbohydrate from 72.27 to 74.47% (YM) and 71.15 to 72.65% (WM). Sodium, magnesium, phosphorous, potassium, calcium, manganese, iron, copper, and zinc were the minerals detected in the <i>mahewu</i> samples, while potassium was the most abundant mineral, having values ranging from 3051.61 to 3283.38 mg/kg (YM) and 2882.11 to 3129.97 mg/kg (WM). Heavy metals detected in this study were all below the recommended tolerable levels by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). Arginine and leucine with values ranging from 0.47 to 0.52 g/100 g (YM) and 0.48 to 0.53 g/100 g (WM) as well as 0.91 to 1.04 g/100 g (YM) and 0.95 to 1.01 g/100 g (WM), respectively, were the most abundant essential amino acids, whereas for non-essential amino acids, glutamic acid, aspartic acid, alanine, and proline were observed to be abundant. Based on the different inocula, the derived <i>mahewu</i> samples prepared using either white or yellow maize have varying nutritional and health beneficial components and the choice of inocula might still be determined by consumer preference.
Marius Eduard Ciocan, Rozália Veronika Salamon, Ágota Ambrus
et al.
One of the earliest biotechnological processes is brewing, which uses conventional raw materials like barley malt and, to a lesser extent, wheat malt. Today, adjuncts are used in the brewing of 85–90% of the world’s beer, with significant regional differences. The results of this study’s brewing were compared to those of beer made only from malted barley. Malted and unmalted sorghum were suggested for use in this study’s brewing. In order to improve the technical mashing operation and raise output yield, commercial enzymes were introduced. The following physicochemical analyses of the finished beer were carried out in accordance with regulatory requirements: original extract (% <i>m</i>/<i>m</i>), apparent extract (% <i>m</i>/<i>m</i>), alcohol content (% <i>v</i>/<i>v</i>, % <i>m</i>/<i>m</i>), density (g/cm<sup>3</sup>), turbidity (EBC), pH, color (EBC), bitterness value (IBU), oxygen content (mg/L), carbon dioxide content (g/L). A nine-point hedonic scale was used to conduct the sensory evaluation of the beer samples. Sorghum was easily included into the technological process to create a finished product that, in many ways, resembled traditional beer, making sorghum appropriate for typical beer drinkers. The laboratory brewing formula that produced the highest-quality results of all the tested variants included 60% sorghum malt and 40% unmalted sorghum: original extract 11.26% <i>m</i>/<i>m</i>, apparent extract 4.59% <i>m</i>/<i>m</i>, alcohol content 4.12% <i>v</i>/<i>v</i>, turbidity 0.74 EBC, CO<sub>2</sub> content 5.10 g/L. The resulting sorghum beer typically has low alcohol content, a complex, aromatic, slightly sour flavor, a mild bitter or astringent sensation, and less stable foam.
Mohamad Zulfadhli Ahmad Sobri, Alya Redhwan, Fuad Ameen
et al.
Biohydrogen production from microalgae is a potential alternative energy source that is now intensively being researched. The complex natures of the biological processes involved have afflicted the accuracy of traditional modelling and optimization, besides being costly. Accordingly, machine learning algorithms have been employed to overcome setbacks, as these approaches have the capability to predict nonlinear interactions and handle multivariate data from microalgal biohydrogen studies. Thus, the review focuses on revealing the recent applications of machine learning techniques in microalgal biohydrogen production. The working principles of random forests, artificial neural networks, support vector machines, and regression algorithms are covered. The applications of these techniques are analyzed and compared for their effectiveness, advantages and disadvantages in the relationship studies, classification of results, and prediction of microalgal hydrogen production. These techniques have shown great performance despite limited data sets that are complex and nonlinear. However, the current techniques are still susceptible to overfitting, which could potentially reduce prediction performance. These could be potentially resolved or mitigated by comparing the methods, should the input data be limited.
Yukun Zhang, Manabu Ishikawa, Shunsuke Koshio
et al.
This study aimed to improve the nutritional value of soybean meal (SBM) by solid-state fermentation (SSF) using <i>Bacillus subtilis natto</i> (<i>B. s. natto</i>) to overcome the limitations of SBM usage in aquafeed. The response surface methodology (RSM) was employed to explore the relationships of fermentation conditions, such as temperature, time, water-substrate ratio, and layer thickness, on the degree of protein hydrolysis (DH) and the crude protein (CP) content. The optimum conditions for achieving the higher DH (15.96%) and CP (55.76%) were 43.82 °C, 62.32 h, 1.08 of water-substrate ratio, and a layer thickness of 2.02 cm. CP and DH in the fermented soybean meal (FSM) increased by 9.8% and 177.1%, respectively, and crude fiber decreased by 14.1% compared to SBM. The protein dispersibility index (PDI) decreased by 29.8%, while KOH protein solubility (KPS) was significantly increased by 17.4%. Flavonoids and total phenolic acid content in FSM were increased by 231.0% and 309.4%, respectively. Neutral protease activity (NPA) also reached a high level (1723.6 U g<sup>−1</sup>). Total essential amino acids (EAA) in FSM increased by 12.2%, higher than the 10.8% increase of total non-essential amino acids (NEAA), while the total free amino acids content was 12.76 times higher than that of SBM. Major anti-nutritional factors in SBM were significantly reduced during the process, and almost all SBM protein macromolecules were decomposed. Together with the cost-effectiveness of SSF, <i>B. s. natto</i>-fermented SBM products have great potential to improve the plant composition and replace high-cost ingredients in aquafeed, contributing to food security and environmental sustainability.